Efficacy of Dapagliflozin in Diabetes Associated Peripheral Neuropathy: A Randomized Placebo Controlled Trial

Diabetic peripheral neuropathy is a length dependent axonal neuropathy that affects at least 50% of patients with diabetes mellitus. It is characterized by sensory loss and pain that initially affects small unmyelinated C fibers which is followed by involvement of the large myelinated fibers as diabetes progresses. DPN is often asymptomatic during the early stages of diabetes ,however, once symptoms and overt deficits have developed, it cannot be reversed. Early diagnosis of neuropathy is thus important because early diagnosis and timely intervention might prevent the development and progression if diabetic neuropathy and might provide us with a means to identify patients at high risk for future complications of DPN which includes risk of foot ulcers and lower limb amputation.

Methods to quantify neuropathy include clinical scores based on symptoms and neurological tests, quantitative sensory testing, electrophysiological measurements, in the form of nerve conduction studies and intraepidermal nerve fiber density in skin biopsy specimens. The neurological examination involves an assessment, such as modified neuropathy disability score, a composite score that assesses touch, temperature and vibration perception and reflexes, which require expert clinical judgement, a strong element of subjectivity and hence poor reproducibility. Neurophysiology is objective and reproducible and is currently considered to be the most reliable measurements for confirming the diagnosis of diabetic neuropathy. However, these measures mainly assess large nerve fibers, making them less sensitive to early DPN,which is more likely to involve the small fibers to begin with.

Objective measures are thus required to accurately determine nerve pathology to detect early stages of DPN, which may be more susceptible to intervention than late-stage sequelae. Small fibers, which constitute 70-90% of peripheral nerve fiber, may be measured in skin biopsies by assessing intraepidermal nerve fiber density, which is considered to be the gold standard for the evaluation of small fibers damage. Indeed, the European Federation of the Neurological Societies and the Peripheral Nerve Society endorse intraepidermal nerve fiber quantification to confirm the clinical diagnosis of small fiber neuropathy with a strong (Level A)recommendation.

Recently, corneal confocal microscopy (CCM), a noninvasive modality for the study of the human cornea, has emerged as a promising technique for the detection of small nerve fiber alterations. CCM is a rapid non-invasive imaging technique for the quantitative assessment of small fiber damage. Several studies have shown that it has good diagnostic utility for sub-clinical DPN, predicts incident DPN and correlates with other measures of neuropathy . Furthermore, automated quantification of corneal nerve parameters allows rapid, unbiased and objective assessment of small fiber damage with comparable diagnostic capability to intraepithelial nerve fiber density (IENFD). Recent data also suggest that CCM shows good reproducibility and could be useful to document nerve regeneration after treatment and simultaneous pancreas and kidney transplantation.

There is currently no Food and Drug Administration (FDA) approved therapy to prevent or reverse human DPN. The current management approach focuses on reasonable glycemic control, and management of associated pain. Sodium-glucose cotransporter 2 (SGLT2) inhibitors as oral hypoglycemic agents have been approved for treating type 2 diabetes mellitus (T2DM). The insulin-independent action mechanism and extra-metabolic benefits of these agents have encouraged ongoing preclinical and clinical trials for evaluating the efficacy and safety of SGLT2 inhibitors. In addition to glucose-lowering effects without hypoglycemia, SGLT2 inhibitors retard the development and progression of diabetic complications. However, it is uncertain whether this effect of SGLT2 inhibitors is due to their glucose-lowering effect or not. In addition, unlike diabetic nephropathy, the effects of SGLT2 inhibitors on diabetic peripheral neuropathy are unexplored.